THERMODYNAMIC ANALYSIS OF GAAS1-XPX VAPOR-PHASE EPITAXY

A model has been developed to analyze the vapor phase epitaxial growth of GaAs1-xPx under different experimental conditions. The deposition process has been explained by a scheme of reactions. The equilibrium c onstant for each reaction has been deduced from thermodynamic data. Th e chemical species considered for the present investigations are AsH, PH, As-2, P-2, As, P, As3P, As2P2, AsP3, AsP, GaCl, AsGaCl, PGaCl, GaA s, and GaP. The growth rates of GaP and GaAs are derived in terms of p artial pressures and deposition temperature by assuming the removal of chlorine from the complex molecules (AsGaCl, PGaCl) as the rate-deter mining step. The phosphorous composition x has been derived from these growth rate expressions. The surface coverage of the adsorbed species as a function of substrate temperature has been investigated. The num erical analysis of our results shows that the composition depends more strongly on partial pressures than on deposition temperature, and As is preferentially deposited compared to P. The validity of our model w as tested by comparing our predictions with reported experimental data , and there is good agreement between them.